unwrap

Is there any way of doing unwrap_or_return an Error (any error)

由 ℡╲_俬逩灬. 提交于 2020-07-10 06:57:18
问题 Is there any way to simplify the returns in the following example (originally copied from here): use std::num::ParseIntError; fn multiply(first_number_str: &str, second_number_str: &str) -> Result<i32, ParseIntError> { let first_number = match first_number_str.parse::<i32>() { Ok(first_number) => first_number, Err(e) => return Err(e), }; let second_number = match second_number_str.parse::<i32>() { Ok(second_number) => second_number, Err(e) => return Err(AnotherError::ParseError("error")), };

Is there any way of doing unwrap_or_return an Error (any error)

由 一笑奈何 提交于 2020-07-10 06:57:10
问题 Is there any way to simplify the returns in the following example (originally copied from here): use std::num::ParseIntError; fn multiply(first_number_str: &str, second_number_str: &str) -> Result<i32, ParseIntError> { let first_number = match first_number_str.parse::<i32>() { Ok(first_number) => first_number, Err(e) => return Err(e), }; let second_number = match second_number_str.parse::<i32>() { Ok(second_number) => second_number, Err(e) => return Err(AnotherError::ParseError("error")), };

Swift: Can't unwrap an optional inside a loop

由 送分小仙女□ 提交于 2020-01-05 04:37:12
问题 I can't understand why unwrapping an optional value is possible in this case: let name: String? = "Toto" guard let name = name else { fatalError() } print(name) but not when this snippet is wrapped in a for-loop: for _ in 0..<100 { let name: String? = "Toto" guard let name = name else { fatalError() } print(name) } I got the error "Definition conflicts with previous value". Using Swift 5 in Xcode 11.0. 回答1: As explained in Why isn't guard let foo = foo valid?, let name: String? = "Toto" guard

Why using implicit unwrap or force unwrap letting the app crash at some stage not beneficial?

由 青春壹個敷衍的年華 提交于 2020-01-05 04:22:06
问题 My point is at some places we know that the variable won't have nil at all but due to some reason we can't instantiate it in the class's init function so we have to make it optional. I also know that we can use optional binding or guard techniques to get rid of it easily. But letting the app crash at some really stupid mistakes because of the implicit unwrap/force unwrap is beneficial for the developers at the developing phase in my opinion . My example would be: class

Swift Optional Dictionary [String: String?] unwrapping error

由 泄露秘密 提交于 2019-12-11 23:33:51
问题 So here I have a basic setup var preferenceSpecification = [String : String?]() preferenceSpecification["Key"] = "Some Key" preferenceSpecification["Some Key"] = nil preferenceSpecification["DefaultValue"] = "Some DefaultValue" print(preferenceSpecification) var defaultsToRegister = [String : String]() if let key = preferenceSpecification["Key"], let defaultValueKey = preferenceSpecification["DefaultValue"] { defaultsToRegister[key] = preferenceSpecification[defaultValueKey]! } But the error

Errors with numpy unwrap when the using long arrays

由 自闭症网瘾萝莉.ら 提交于 2019-12-11 13:07:08
问题 I am trying to use the function numpy.unwrap to correct some phase I have long vector with 2678399 records which contains the difference in radians between 2 angles. The array contains nan values although I think is not relevant as unwrap is applied to each record independently. When I applied unwrap, by the 400 record generates nan values in the rest of the array If I apply np.unwrap to just one slice of the original array works fine. Is that a possible bug in this function? d90dif=(df2['d90

Error: Found nil while unwrapping an Optional value; While Pass Data to the New Controller [duplicate]

由 拈花ヽ惹草 提交于 2019-12-11 04:11:12
问题 This question already has answers here : Unexpectedly found nil IBOutlet in prepareForSegue (2 answers) Closed 3 years ago . I'm learning swift 2. I'm trying to pass the data of the cell (UITableView) that is tapped to the new View Controller. But I constantly get the error of: " unexpectedly found nil while unwrapping an Optional value " for the code line " destination!.label.text = valueToPass ". Below is my code. May I know what should I do to solve it? I have spent hours but still stuck

solving a singular matrix

由 假如想象 提交于 2019-12-10 11:29:05
问题 I am trying to write a little unwrapper for meshes. This uses a finite-element-method to solve for minimal linear stress between flattened and the raw surface. At the moment there are some vertices pinned to get a result. Without this the triangles are rotated and translated randomly... But as this pinning isn't necessary for the problem, the better solution would be to directly solve the singular matrix. Petsc does provide some methodes to solve a singular system by providing some

solving a singular matrix

由 此生再无相见时 提交于 2019-12-06 13:49:09
I am trying to write a little unwrapper for meshes. This uses a finite-element-method to solve for minimal linear stress between flattened and the raw surface. At the moment there are some vertices pinned to get a result. Without this the triangles are rotated and translated randomly... But as this pinning isn't necessary for the problem, the better solution would be to directly solve the singular matrix. Petsc does provide some methodes to solve a singular system by providing some information on the nullspace. http://www.mcs.anl.gov/petsc/petsc-current/docs/manual.pdf#section.4.6 I wonder if

“Value of optional type 'String?' not unwrapped; did you mean to use '!' or '?' ?”

由 不羁岁月 提交于 2019-12-05 17:30:29
问题 I have not been studying iOS or Swift for very long. With one of the latest Xcode updates, many of the apps I have made on my computer now appear to be using obsolete syntax. Xcode talks us through converting it to new syntax but often that does not solve anything and I have a new problem. Here is code for one of the first app I made after the syntax has been converted. I am getting an error saying: Value of optional type 'String?' not unwrapped; did you mean to use '!' or '?' ? I know this
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